Gas leak under control, but steps remain until it's sealed

LOS ANGELES (AP) — A utility company got control of a leaking well that spewed natural gas for nearly four months and uprooted thousands of Los Angeles residents. Here's a look at what needs to be done to seal it permanently and what happens after the state certifies the well is dead.

WHAT WAS THE PROBLEM?

Southern California Gas Co. reported in October that gas was leaking from a storage well at its Aliso Canyon facility.

FILE - In this Nov. 3, 2015, file photo, provided by Southern California Gas Co., SoCalGas crews and technical experts attempt to safely stop the flow of natural gas leaking from a storage well at the utility¿s Aliso Canyon facility near the Northridge section of Los Angeles. The utility says it has stopped the natural gas leak near Los Angeles after nearly 4 months. (Javier Mendoza/SoCalGas via AP, File)

The leak occurred in a well drilled in 1953 to pump oil from beneath the Santa Susana Mountains. After wells in the area ran dry, the field was converted in the 1970s to store natural gas.

Wells are used to pump gas underground for storage and then withdraw it when demand spikes.

The facility, which has 115 wells and is capable of supplying gas for all of Southern California for more than a month, is the largest natural gas storage facility west of the Mississippi River.

WHY DID IT TAKE SO LONG TO STOP THE LEAK?

Initial efforts to stop the leak failed because gas was escaping at pressures exceeding 2,600 pounds per square inch, preventing a mix of muddy slurry from being pumped into the leaking well.

After several failed attempts by well control experts from Boots & Coots Services, the company that helped extinguish oil well fires in Kuwait during the 1991 Gulf War, workers began drilling a relief well in December to intercept the leaking well.

Penetrating the well a mile-and-a-half underground took more than two months as drilling was regularly suspended and equipment withdrawn from the relief well so a magnetic tool could be fed into the pipe to make sure they were on target to hit the leaking well.

Workers intercepted the leaking well Thursday where it enters the gas storage reservoir deep underground and pumped mud and heavy fluids to block the leak.

WHAT ARE THE NEXT STEPS?

The company was to begin pumping cement down the relief well as soon as Friday to permanently seal the leak, said Jimmie Cho, a SoCalGas senior vice president.

After the cement dries, which could take several days, a five-part test that includes measuring temperature and pressure down the well and using a microphone to listen for leaks will determine if it is sealed. The state will also use air quality monitors and infrared cameras to make sure no methane is escaping.

Once inspectors with the state Division of Oil, Gas, and Geothermal Resources certify the well is dead, investigators will try to find the cause of the blowout.

HOW SOON WILL RESIDENTS BEGIN RETURNING HOME?

When the well is permanently sealed, the gas company is required to pay seven more nights of lodging for those living in hotels or reimbursing those staying with family or friends. Residents who relocated to apartments and rental houses will be able to stay through leases as late as April 30.

Many people have already returned home. Of 6,400 households that were relocated, mostly from the Porter Ranch section of L.A., some 1,700 have returned, the gas company said.

Others, however, remain skeptical and wary of returning.

The gas company originally set a two-day return period for those in short-term housing. While the Los Angeles city attorney negotiated an extension to seven nights, other lawmakers and residents are pushing for a 30-day return period.

FILE - This Dec. 17, 2015 file photo provided by Earthworks shows an overhead aerial view of the relief well at the Aliso Canyon facility above the Porter Ranch area of Los Angeles. The utility says it has stopped the natural gas leak near Los Angeles after nearly 4 months. (Pete Dronkers/Earthworks via AP,File)

FILE - In this Dec. 9, 2015, pool file photo, crews work on stopping a gas leak at a relief well at the Aliso Canyon facility above the Porter Ranch area of Los Angeles.The utility says it has stopped the natural gas leak near Los Angeles after nearly 4 months. (Dean Musgrove/Los Angeles Daily News via AP, Pool, File)